1. Field of the Invention
The present invention relates to a spinning washer for washing and removing debris from semiconductor wafers and other workpieces after being ground.
2. Related Arts
Semiconductor wafers and other workpieces are prone to be contaminated with debris after being ground. It is, therefore, necessary to wash and remove debris from such contaminated semiconductor wafers by using a spinning washer as shown in FIGS. 7 and 8.
In the spinning washer 50, the spinning table 51 holds fixedly a semiconductor wafer W, and the spinning table 51 is rotated at a high speed while flushing water from the water nozzle 52. Etching liquid can be supplied from the etching liquid nozzle 53 to the semiconductor wafer W to meet occasional demands.
After washing, the spinning table 51 continues rotating at the increased speed while the air nozzle 54 ejects air at an increased pressure, thereby drying the semiconductor wafer W.
As seen from FIG. 8, the semiconductor wafer W is often larger than the spinning table 51, so that the semiconductor wafer W may be held only at its center area. The circumferential area of the semiconductor wafer W extending beyond the underlying spinning table 51, therefore, is not stable, and when exposed to the flushing water or blowing air, the circumferential area of the semiconductor wafer W is prone to be deformed or broken.
As the recent tendency, semiconductor wafers have been decreasing less and less in thickness to meet the ever increasing demand for reducing to possible minimum the size and weight of cellular phones, note-sized personal computers and other electronic devices. Sometimes, semiconductor wafers are ground to be 100 microns or less thin. Such thin wafers are likely to be broken while being washed or dried.
Referring to FIG. 9, an adhesive tape T is applied to one side of the semiconductor wafer W, and the semiconductor wafer is laid on the holding table 55 with its tape T down. As seen from the drawing, the holding table 55 is larger than the semiconductor wafer W. A negative pressure is applied to the semiconductor wafer W so that it may be fixedly held on the holding table 55. Then, the semiconductor wafer W is subjected to grinding with a grindstone 57. Debris is produced by grinding the semiconductor wafer W to be sucked to the holding table 55 as the negative pressure prevails therearound. Thus, the circumferential side 56 of the semiconductor wafer W is contaminated with debris.
When the washing is effected as in FIG. 8, debris can be removed from the surface of the semiconductor wafer W, but debris can be hardly removed from the circumferential side 56 of the semiconductor wafer W, allowing the debris to be stuck to the circumferential side 56, thus making it difficult to peel the adhesive tape T off from the semiconductor wafer W at a later step.
One object of the present invention is to provide a spinning washer which can wash the opposite surfaces as well as the circumferential side of a semiconductor wafer without the fear of breaking the semiconductor wafer no matter how thin it may be.
To attain this object a spinning washer according to the present invention comprises: a spinning table for fixedly holding a wafer, the spinning table being capable of turning at a high speed; water flushing means for flushing water to the wafer held on the spinning table; first brush means which can be put in coplanar position relative to the upper surface of the wafer around the circumference of the spinning table; and second brush means confronting the first brush means, the second brush means being adapted to be selectively put in operative or inoperative position, the second brush means being put in contact with the upper surface of the wafer in the operative position.
The first brush means may comprise an annular base having its outer diameter larger than that of the wafer, and an opening made at its center, the opening being large enough to allow the spinning table to pass freely therethrough, a first stiff-hair section stuck on the upper surface of the annular base, and a first piston-and-cylinder for raising or lowering the annular base, thereby putting the first stiff-hair section in the operative or inoperative position, when put in the operative position, the first stiff-hair section being yieldingly depressed by the overlying wafer, leaving the circumferential stiff-hair part upright, surrounding closely the circumference side of the wafer.
The second brush means may comprise a disk, a second stiff-hair section stuck on the lower surface of the disk, an arm holding the disk rotatably, a second piston-and-cylinder for raising or lowering the arm, thereby putting the second stiff-hair section in operative or inoperative position, and a drive unit for rotating the second piston-and-cylinder thereby to swing the arm and hence the second brush, when put in the operative position, the second stiff-hair section being pushed against the upper surface of the wafer, thus sandwiching the wafer between the first and second stiff-hair sections.
Other objects and advantages of the present invention will be understood from the following description of a spinning washer according to one preferred embodiment of the present invention, which is shown in accompanying drawings.